Datasheet

28.9.1 ADC Multiplexer Selection Register
Name: ADMUX
Offset: 0x7C
Reset: 0x00
Property: -
Bit 7 6 5 4 3 2 1 0
REFS[1:0] ADLAR MUX[3:0]
Access
R/W R/W R/W R/W R/W R/W R/W
Reset 0 0 0 0 0 0 0
Bits 7:6 – REFS[1:0] Reference Selection
These bits select the voltage reference for the ADC. If these bits are changed during a conversion, the
change will not go into effect until this conversion is complete (ADIF in ADCSRA is set). The internal
voltage reference options may not be used if an external reference voltage is being applied to the AREF
pin.
Table 28-3. ADC Voltage Reference Selection
REFS[1:0] Voltage Reference Selection
00 AREF, Internal V
ref
turned OFF
01 AV
CC
with external capacitor at AREF pin
10 Reserved
11 Internal 1.1V voltage reference with external capacitor at AREF pin
Bit 5 – ADLAR ADC Left Adjust Result
The ADLAR bit affects the presentation of the ADC conversion result in the ADC data register. Write one
to ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the ADLAR bit will
affect the ADC data register immediately, regardless of any ongoing conversions. For a complete
description of this bit, refer to ADCL and ADCH.
Bits 3:0 – MUX[3:0] Analog Channel Selection
The value of these bits selects which analog inputs are connected to the ADC. If these bits are changed
during a conversion, the change will not go in effect until this conversion is complete (ADIF in 28.9.2
ADCSRA is set).
Table 28-4. Input Channel Selection
MUX[3:0] Single Ended Input
0000 ADC0
0001 ADC1
0010 ADC2
0011 ADC3
0100 ADC4
ATmega48PA/88PA/168PA
Analog-to-Digital Converter (ADC)
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40002011A-page 326